I could've sworn he was a US Army Ranger serving in South America (GitS:SAC, episode 10), then he's later later part of the JGSDF in Saito's flashback (GitS: SAC 2nd GiG, episode 14) alongside Motoko Kusanagi and several others.

There are also references to this in GitS:SAC episode 16 when he infiltrates a US military base.

I could be wrong but I'm 100% positive he's Caucasian. I'll get the DVDs out later and see if I can verify.

Edit: Alright, I see where you're coming from and in context you're probably right. I'm going off Batou's use of the English word "Rangers" (but it's possible that's a loan-word in Japanese) and this screencap from GitS:SAC episode 10.

They all look like stereotypical US Military to me. I haven't checked the other episodes yet.

Yeah, I do remember those scenes. There's also the possibility of him joining the United States Army Rangers as an individual from a foreign country (which would be Japan in this case). There are foreign soldiers in the Army Rangers now, I know that much.